According to sleep experts, lost sleep hurts learning and hinders school-day success. That’s bad news, because today’s kids get about an hour less sleep each night than they did 30 years ago, says New York Times bestselling author Po Bronson in his book NurtureShock: New Thinking About Children. This lost sleep comes with a steep price tag — impaired learning and academic success.

How does sleep boost learning? Researchers believe it has to do with the way the brain processes information during sleep. In fact, Michigan State University researchers found that children can even learn while they’re asleep as the brain integrates new information and memories. Researchers from University of Florida discovered that newborns learn in their sleep, and new research from the American Academy of Sleep Medicine shows that sleep helps students perform better on tests.

Read on for age-specific information on how sleep impacts learning — and how to help kids get a better night’s rest.

EARLY SCHOOL YEARS • Ages 3 to 7

For sleep-deprived kids, school trouble starts early: 10 percent of kids in early education suffer from sleep disturbances that disrupt learning, according to a German study. The American Professional Sleep Society reports that sleep deprivation significantly worsens inattentiveness and hyperactivity in young children, leading to ADHD-like symptoms (known as “faux” ADHD).

Even modest sleep deprivation is enough to hinder learning. According to a study published in the journal SLEEP, a mere hour of lost slumber is enough to bring on inattentiveness and hyperactivity in young children. A 2011 study of 6- and 7-year-olds shows that language skills, grammar, spelling, and reading comprehension suffer when kids get less than nine hours of sleep per night.

How much sleep to kids need?

10 to 12 hours per day

How to help:

Sleep-deprived children may not appear sleepy, says Shelby F. Harris, Psy.D. , director of the Behavioral Sleep Medicine Program at Montefiore Medical Center in New York. In fact, they may act hyper and goofy. But preschoolers and school-age children don’t outgrow the need for a consistent bedtime and bedtime routine. Establish an age-appropriate bedtime that allows your child to rest for 10 to 11 hours each night.

TWEEN YEARS • Ages 7 to 12

During the late elementary- and middle-school years, academics become more challenging and sports more competitive. But when increasingly busy schedules start cutting into sleep, kids retain less of what they learn, says Mark Splaingard, M.D., director of the Sleep Disorders Center at Nationwide Children’s Hospital. “Long hours spent on sports practice or math problems are counterproductive, if these activities keep kids up late at night,” he notes. Kids will learn more and perform better with sufficient shut-eye.

How much sleep do they need:

10 to 11 hours per day

How to help:

Parents need to understand sleep’s importance. That means maintaining firm school-year bedtimes and choosing after-school and evening activities that end at least an hour before kids need to wind down for bed.

TEEN YEARS • Ages 13 to 18

Teenagers are Splaingard’s most sleep-deprived patients, a fact that doesn’t surprise him. During high school, after-school jobs, extracurricular activities, sports, socializing, and homework simply don’t leave enough time for sleep. Most teens need more than nine hours a night, and chronic sleep deprivation hurts learning at a time when kids need lots of mental energy for tougher subjects.

But busy schedules deserve only part of the blame for teens’ sleep deficits: cell phones and laptops keep kids up late, often into the wee hours. When teens finally power off their computers and go to bed, round-the-clock access to cell phones or gaming systems disrupts sleep, especially when teens are ‘on call’ with friends. Sleep disruption adds up to bleary mornings and bleak report cards.

How much sleep do they need:

8 to 9 hours per day

How to help:

Protect teens’ precious sleep hours with a media curfew — shut down all electronics one hour before bed and establish a charging station outside the bedroom where teens leave their electronics overnight. This important step keeps bedrooms free of sleep-disrupting cell phones and computers, says Harris. “The bedroom should be a place for sleep,” she notes. “It’s not a spot for homework, watching TV, or surfing the Internet.”

When it comes to learning, tutors, cutting-edge gadgets, and hours of homework can’t compensate for hours of lost sleep. When parents prioritize kids’ sleep needs, learning comes more naturally, says Splaingard. “We think we’re helping make kids more successful with more activities and more homework. But what they really need is more sleep.”

Malia Jacobson is a nationally published journalist and mom of three. Her latest book is Sleep Tight, Every Night: Helping Toddlers and Preschoolers Sleep Well Without Tears, Tricks, or Tirades.